Alternative TDMS symbol and no file tree

[TGL]

Hi,

I am logging measurement data at 100 Hz in a TDMS file using a labview program. When I create a file for longer than about 5 minutes the icon in the data finder in Diadem is different and it takes significantly long to load the data and there is a message in the channel preview saying "channel preview terminated". I have attached a screenshot of the icon and channel preview in DIAdem. Has anyone ever come across this before?

Cheers

[winner]

That is a feature. Because the TDMS file has about 8 million values DIAdem would need a significant time to create the preview. Therefore the preview will be terminated automatically.

In the help you found the following information (Help Tree: Basics > DIAdem NAVIGATOR > Symbols in the File Browser) 
Time exceeded for indexing: DIAdem was not able to index the file within the specified time. You can change the time that DIAdem uses to index a file on the "Indexer" tab in the Configure My DataFinder dialog box. You cannot change this time for a remote DataFinder.

Hope this helps

Winfried

[AndreasK]

If the file needs some time to open it is potentially fragmented (containing a lot of single written elements) at the end of the measurement.

Maybe you could call the defragment method in labview after your measurement ended. This should potentially make your files indexable by the datafinder.

Please make sure the tdms_index file exists after measurement.

Greetings

Andreas

[TGL]

So can I just increase the timeout per file (in s) to as large a value as required to fully index the file? And is there anyway to configure DIAdem to create the full preview?

If I use the defragment command does that mean I will lose zero values?

[AndreasK]

The defrag is lossless. It just merges chunks that where added during measuring the file.

header 1, data 1

header 2, data 2

header 3, data 3

header 4, data 4

header 5, data 5

...

will be converted to

header 1, data 1 ,data 2, data 3, data 4, data 5

So instead of having to jump a lot over the file data can be accessed in one piece because after defrag file is sorted and optimized for analyzation.

Because of this it will open faster and potentially you do not have to change the timeout at all.

Greetings

Andreas

[TGL]

where do it put the defragment tdms vi? Is it best to place it after the write vi's but before the close vi? And can it be placed outside the while loop?

[AndreasK]

Please place it outside of the while loop and after the close.

Its postprocessing for the file.

[TGL]

Ok, but when I do this the index file is still pretty huge (of a similar size to the TDMS data file). So when I drag the file into DIAdem it still takes a while to load in the data portal. Should this be the case or should the index file be compressed once the loop has stopped?

[TGL]

Also, I should add - I am opening and closing TDMS files within the loop as I am writing a new file every hour. So is it still ok just to have the one defrag TDMS vi outside the main while loop?

[Brad_Turpin]

Hi TGL,

You need to defrag each of your TDMS files.  If you're creating multiple segmented data files, then you need to defrag each of them after they are closed.  If your index file and TDMS file are roughly the same size, then either your TDMS file is really small (kB) or the TDMS file is still fragmented.

You can simply increase the indexing timeout per file in the DataFinder configuration in order to have the fragmented TDMS files successfully indexed, but the preview graph will always display slower if the TMDS file is fragmented.

Brad Turpin

DIAdem Product Support Engineer

National Instruments